The present disclosure generally relates to semiconductor structures, and particularly to semiconductor-on-insulator (SOI) field effect transistors having raised source/drain regions, and methods of manufacturing the same.
Extremely thin semiconductor-on-insulator (ETSOI) field effect transistors are leading candidates for advanced semiconductor devices for enabling continuous scaling of planar semiconductor technology. Successful manufacture of ETSOI field effect transistors requires integration of n-type metal oxide semiconductor (nMOS) field effect transistors and p-type metal oxide semiconductor (pMOS) field effect transistors onto a same semiconductor substrate, while maintaining high performance and low leakage current.
A key feature to improve performance and reduce series resistance in ETSOI field effect transistors is the use of raised source drain (RSD) epitaxy, which enables formation of thick low-resistance source and drain regions on a thin top semiconductor layer of an ETSOI substrate. Ideal junction design for ETSOI field effect transistors with RSD involves low source and drain (S/D) resistance, low source and drain extension resistance, and good physical connection between the source and drain regions and the source and drain extension regions that provides a low resistance connection therebetween.
One of the challenges in manufacture of the ETSOI field effect transistors is the amorphization of a single crystalline semiconductor material during ion implantation for formation of source/drain extension regions. Because the thickness of a top semiconductor layer in an ETSOI substrate can be on the order of 5 nm and it is very difficult to provide an implantation depth less than 5 nm, ion implantation intended to provide electrical dopants into source/drain regions can completely amorphize the semiconductor material in the implanted region down to the interface with a buried insulator layer and prevent recrystallization of the implanted source and drain extension regions into single crystalline regions. In order to provide low resistance in source and drain extension regions, therefore, the source and drain extension regions need to recover a single crystalline structure during a regrowth process after ion implantation.